Downstrike — the weather word for a lightning bolt that hits the
ground. A live lightning map centered on your home. No accounts, no sign-ups: everything runs
in your browser, using free public data.
01 · How the lightning is tracked
Strikes come from Blitzortung.org,
a worldwide network of radio receivers run by volunteers. Nobody points a camera at the sky —
the network hears every bolt and finds it with a stopwatch:
- A lightning bolt is a radio transmitter. Its huge burst of electric
current sends out a radio pulse that travels thousands of kilometres at the speed of light.
(It's the crackle you hear on AM radio during a storm.)
- Volunteers listen at home. Each station is a small antenna kit with a
GPS clock accurate to a millionth of a second, which records the exact moment the pulse
arrives.
- Timing finds the bolt. Radio travels about 300 metres every
microsecond, so stations farther away hear the pulse a little later. Compare arrival times
at four or more stations and the possible locations cross at one point: the strike. It's
GPS in reverse — many receivers timing one flash to find it.
- Usually 20–40 stations hear each strike, pinning it to about a
kilometre. It reaches your screen 5–15 seconds after the real flash.
Downstrike keeps a live connection to this feed and receives every
located strike on Earth — often 50+ per second. Because it's a volunteer network, a strike
is occasionally missed or placed a kilometre or two off. The data is free for personal use.
02 · What's on the map
- Strike dots. A new strike lands with a white flash, then cools like an
ember — the color tells you its age:
now
2 min
8 min
16 min
30 min, then gone
So a storm paints its own trail: white at the front, embers behind.
- Thunder rings. Each strike sends out a ring growing at 343 m/s — the
real speed of sound. When a ring crosses your house, that's the exact moment you'd hear the
rumble.
- Home rings. Dashed circles at 10, 25 and 50 km show distance at a
glance. The amber glow on the outer ring points toward recent strikes and brightens as a
storm gets closer.
- WIND. Hundreds of particles drift with the real wind (live data,
refreshed every 30 minutes).
- RADAR. Live rain radar, refreshed every 5 minutes, off by default.
(The free tiles get blurry if you zoom way in.)
03 · The thunder sound
The thunder is generated live by code — no recordings — and shaped by the strike's real
distance, the same way air shapes real thunder:
| Layer | What it is | When you hear it |
|---|
| Boom | A deep, blunt impact with an echo |
Only within ~12 km — harder the closer the strike |
| Sub-bass thump | A low 50 Hz punch you feel |
Within ~25 km |
| Rumble | A rolling growl with random peaks |
Always — it's all that's left of a far-away strike |
The farther the strike, the quieter it gets (about 10× softer by 50 km), the deeper it
sounds (air soaks up the high notes first), and the longer and slower it rolls. Flip
SOUND on to hear a preview — browsers need one click on the page before
they'll play audio.
04 · The controls
- The top strip. One line with the essentials — closest strike, strikes
per minute, wind, and rain. Tap it to open the full detail cards.
- The icon row. Bell = storm warnings (iOS app). The radar, wind and
sound icons toggle those layers. The house brings you back home (press it at home to
change your address), and the sliders icon opens Settings — that's where the alert
distance lives (5–50 km; any strike inside it fires the red banner and thunder at that
strike's real distance).
- The big glowing bolt is ⚡ STORM — our favorite button, so it's the
big one. One press flies you to the most active storm on Earth right now; press again to
hop to the next. Away from home, you hear what you'd hear standing at the crosshair in the
middle of the screen: any strike inside its dashed 50 km ring plays at its real
distance.
- ALERTS (iOS app). Turn it on and your phone gets a push notification
when the National Weather Service issues a severe thunderstorm or tornado warning for
where you are — even with the app closed. These are the official warnings, checked every
few minutes.
- Next hour rain (iOS app). A minute-by-minute strip showing when rain
will start and stop at your location over the coming hour, powered by
Weather.
05 · Privacy & sources
Your address is looked up once and saved only in your browser. No accounts. Visits are
counted with GoatCounter, a privacy-friendly counter that uses no cookies and collects no
personal data.
One exception, and only if you turn on ALERTS in the iOS app: your
device's push token and your location rounded to about a kilometre are stored on our server,
because something has to check the warnings while your phone is asleep. Nothing else is
stored, and turning ALERTS off stops the checks.
| What | Source | Cost |
|---|
| Lightning strikes | Blitzortung.org community network | Free (personal use) |
| Basemap | CARTO dark-matter · OpenStreetMap | Free |
| Wind | Open-Meteo | Free |
| Rain radar | RainViewer | Free (zoom-limited) |
| Geocoding | OSM Nominatim | Free, used once |
| Visit counter | GoatCounter (no cookies) | Free |
| Storm warnings (iOS) | National Weather Service | Free |
| Rain nowcast (iOS) | Apple Weather / WeatherKit | Free |
06 · Credits
Downstrike was designed and created by Leo and Noah Zimmerman, with help
from Claude. Strike data flows thanks to the volunteers of the Blitzortung.org network.